This renewal proposal for our Program Project Grant continues to employ an interdisciplinary approach to study the functions of protein-glycan interactions in the vascular system. The three thematically related projects are led by investigators with complementary expertise and a strong published record of collaborative research. Project 1 uses gene-targeted mice to study the interplay of adhesion and signaling molecules in the vasculature. The emphasis is on processes that regulate the interactions of selectins with their glycoconjugate ligands, a critical early response during inflammation and thrombosis. Mice with altered expression of selectins, selectin ligands, or signaling proteins will be studied. Project 2 studies the interactions of galectins with leukocytes. Major themes include the defining the glycan structures recognized by each galectin, the signaling mechanisms for the novel exposure of phosphatidylserine on activated neutrophils without apoptosis, and the biological roles of galectins in regulating inflammation in vivo. Project 3 studies how the 0-glycoprotein podoplanin maintains separated blood and lymphatic vessels, how mixing of blood and lymphatic vessels contributes to disease, and how 0-glycosylation regulates the functions of podoplanin in vitro and in vivo. There is unusually high synergy among the projects that results from the intellectually overlapping themes and the sharing of reagents and methods. An administrative core cements the interactions, in particular through maintenance of a server for data exchange among the projects and through computer support for processing images and other complex data. The data obtained will enhance our understanding of the functions of lectins and glycoconjugates during inflammation, thrombosis, and vascular development. This information may suggest new approaches to treat heart attacks, strokes, and other cardiovascular disorders.